Multiple horn feed for parabolic reflector with phase and power adjustments



Feb. 8, 1966 J. BARTHOLOMA ETAL 3,234,559

MULTIPLE HORN FEED FOR PARABOLIC REFLECTOR WITH PHASE AND POWER ADJUSTMENTS 4 Sheets-Sheet 1 Filed April 27, 1961 S m R m m E T. V C m E L E 3 R I O llrlv b Jlok llk l 0 m H POWER "DIVIDER- ATTORNEY Johann Bcrtholomfi 8\ Heinz Brunner 1966 J. BARTHOLOMA ETAL 3,

MULTIPLE HORN FEED FOR PARABOLIC REFLECTOR WITH PHASE AND POWER ADJUSTMENTS Filed April 27, 1961 4 Sheets-Sheet 2 Fig.3

2 Fig.2

mvsmons Johann Burtholoma 8 Heinz Brunner ATTORNEY 8, 1966 J. BARTHOLOMA ETAL 3,

MULTIPLE HORN FEED FOR PARABOLIC REFLECTOR WITH PHASE AND POWER ADJUSTMENTS Filed April 27, 1961 4 Sheets-Sheet 3 I Is ISb' R TRANSMISSION GEAR SERVOMOTOR REMOTE FIX 0 POSITION CONTROL SELECTOR MEANS MEANS INVENTOR FIG 6 Johann Bortholomfia Heinz Brunner fw/wl/ ATTORNEY Feb. 8, 1966 J. BARTHOLOMA ETAL 3,234,559

MULTIPLE HORN FEED FOR PARABOLIC REFLECTOR WITH PHASE AND POWER ADJUSTMENTS Filed April 27. 1961 4 Sheets-Sheet 4.

mvsrvrons Johann Bortholomt'l 8 United States PatentO v The present invention relates to a radiator including several hornexciters and reflector means for producing an adjustable directional pattern, and in particular, one having a cosec shape.

For the purpose of producing asymmetrical directional antenna propagation patterns employing reflectors excited by horns, .it is known in the prior art to give the reflector an asymmetrical design and to use horn exciters, arranged in a line in front of a parabolic reflector, and to ,produce the desired pattern by delivering different power outputs to the exciters in the required mutual phase 're- -lationship. Each individual horn of this line may be considered substantially as a point source having as a consequence its own sharply beamed primary directional pattern contributing to the secondary directional propagation pattern. The angular spread of the individualhorn primary directional patternsgiving. by superposition the, resulting composite secondary pattern-from .the main axis of the parabolic reflector is a function of .the amounts of offset of the position of the individual horns from this main axis.

The power division and the corresponding phase adjustments of these known horns are established -by-their construction once and for all, for example, by ,projecting separator sheets into the .mainwaveguide or by the selection of the lengths of theiridividualcoupling waveguides supplying the individual horns. i

The invention is addressed to the purpose of providing a directional antenna having a selectively and easily adjustable complex directional propagation pattern espe- .cially one having a cosec shape.

Theinvention comprises for this purpose a device for producing a complex directional pattern including several exciters, preferably horns, arranged in a line and directed intoa common reflector, the ,individualexciters .being coupled to a feeder line'through adjustable power dividers and phase shifters, whicli'can beadjustedto provide a uniformphase. front directed into the reflector by said horns.

Such an antenna may be used to particular advantage, for example, as an elevation searching antenna insocalled precision aircraft-approach radar installations since its directional pattern, having preferably a cosec shape, is particularly suited to such purpose by installation of the antenna next to the landing strip. The easy adjustability of the directional pattern of the antenna according to the invention makes it possible to adapt it to the ambient local conditions by producing such a directional pattern as to discriminate against obstructionsfor example, structures standing near the landing strip, which ability is of advantage especially .in the case of mobile radar stations.

Additional objects and advantages of the present invention will become apparent upon consideration of the following description when taken in conjunction with the accompanying drawings in which:

FIGURE 1 schematically illustrates an exciter for a parabolic reflector comprising five horns arranged in a line and coupled to supply lines in accordance with the invention.

FIGURE 2 shows in cross section an enlarged adjustable power divider of the type used in FIGURE 1'.

3,234,559 Ratented Feb. 8, 1966 FIGURE 3 is a cross-sectional view of the power divider according to FIGURE Z taken along the line 3--3. FIGURE 4 is a sectional view through a modified embodiment according to the invention.

FIGURE 4a' is a sectional view taken on line 4a- 4 a of FIGURE 4. FIGURES is a graphical representation of the pattern obtained by means ofv the exciter according to FIG- URE l for, producing a ,cosec -shaped characteristic from which the elementary directional patterns of the individual horns and. their resulting-directional patterns may be read off.

FIGURE 6 schematically illustrates, part of a further embodiment according to the inventioncomprising remote-control means.

Referring now to FIGURE 1, the horn exciter according to the invention consists of live individual horns 1 to 5, arranged in a line side-by-side, and the axes 6, 7 8, 9, and 10 of these horns are arranged in, such a Way that theyjmeet at av comrnonpoint on the mirror surface of a parabolie'reflector R placed in front of these horns, the distance betweenthe horns and the reflector being shown disproportionatelysmall, to permit illustration. Thehorns are connected to a common supply waveguide 16 through curved coupling waveguides 11, 12, 13, 14, and 15. The desired adjustable power division between the individual horns is accomplished by power dividers 17a, 17b, 17c, and-17d. The variable adjustment of the phase of the energy supplied to the individual horns is accomplished by phase shifters 18a, 18b, 18c, and 18d.

- FIGURE 2 shows. gttypical power divider 17c according to FIGURE ilit on an enlarged scale. The curved coupling waveguide 13, for example, is connected thereby to the supply waveguide 16. A resilient bronze sheet 19, about 0.2 mm. thick divides the tapped-off energy from the main part of .thewaveguide 16, the remaining portion of which energy travels on .tofthe upper part of this .Waveguide through the guide 16a, and the tapped-off sheet 19. is fixed alongits edges 25 to the waveguide 16, but is provided with corrugations 24 so as to permit elastic deformation thereof by the adjusting screws, in

order to change the spatial position of the center of the sheet to obtain the power division desired, the edges 25 of the bronze sheet 19 being solidly connectedwith the.

narrow sides 26 and 27 ofthe sup-ply waveguide 16. It is thus apparent that the power dividers are infinitely, i.e., steplessly, variable.

The glass-fiber pins 22 and 23 have some tendency to disturb the electromagnetic fields, but these interference effects may be cancelled by compensation pins,28, for example also comprising glass-fiber pins, arranged at a distance -of mi/4, where 11 1, 3, 5, and A is a propagation wavelength in the waveguide. Preferably, however, this spacing will be A/ 4 from these points of interference. l

The phase shifters 18 shown in FIGURE 1 are known per se. They comprise a dielectric material, for example a material known as Polystyren, and take the form of disks mounted in pairs and having a width corresponding substantially to the internal dimensions of the narrower sides 26, 27 of the supply waveguide 16. These disks taper off at both ends in a wedge-shaped manner in order to reduce reflections of the electromagnetic waves reaching them. By adjusting means which are not shown in detail, such as screws and glass-fiber pins, these phase shifters are displaceable perpendicular to the plane of drawing of FIGURE 1 by moving the pairs of phase shifters towards one another in such a way, that any desired phase shift between and 360 is possible at each individual phase shifter. Of course, any other suitable phase shifters may be used instead of the phase shifters 18 shown herein by way of example.

FIGURES 4 and 4a show a more compact embodiment of the invention wherein the horns 1 to 5 of FIG- URE 1 do not have to be connected to the supply waveguide through curved coupling waveguides 11 to 15 but may be fixed directly at their tapered ends to the supply waveguide. This embodiment is illustrated in cross section through part of such a device. A horn 3' is directly connected with a supply waveguide 16, containing also phase shifters 18b, 18c similar to shifters 18 according to FIGURE 1. The coupling of power to the horn 3' is by way of a slit 29 in the broad side of the supply waveguide 16', which slit does not have to extend over the entire width of the waveguide. In order to adjust the effective length of the slit, a cylindrical screw 31 is provided between a disk 30 of low-loss material, such as Teflon, arranged in the horn and the slit 29 through the waveguide in such a way that, depending upon the position of the screw, it more or less covers the slit. As shown in FIGURE 4a such screws 31 may be provided in front of each slit, thus making possible any desired degree of covering of the slit 29, which covering is always symmetrical and provides a definite power division.

FIGURE 5 graphically shows a directional pattern, in this case one having a cosec shape, adjustable with the device according to the invention, for example as shown in FIGURE 1, plotting relative field strength E against the angle a made with the main axis of radiation. The solid curve 32 gives the desired pattern; curve 33 shows the characteristic curve of horn 3 according to FIGURE 1; curve 34 shows that of horn 2 according to FIGURE 1; curve 35 that of horn 1 according to FIGURE 1; and curve 36 shows the composite directional pattern resulting from the blending of the individual characteristics to produce an over-all characteristic. The measured deviations of the resulting directional pattern from the theoretical desired values lie in each case below 2 db, and usually even below 1 db. During the independent measuring of the individual horn characteristics for the purpose of plotting curves 33, 34, 35, all horns except the one under consideration were covered with low-reflection power-absorbing material so that they did not contribute to the radiation. The composite characteristic, resulting from the superposition of the individual characteristics of the horns 3, 4 and 5 of the device according to FIGURE 1, is not shown in FIGURE 5, since it is merely a mirror image of the curves shown for the horns 1, 2 and 3.

FIGURE 6 schematically illustrates a part of a further embodiment according to the invention. As indicated by the same numbers of the parts the power divider according to FIGURE 6 is similar to that shown in FIGURE 2. Instead of the adjusting screw 20, however, there is provided a spring 37 which presses the glass-fiber pin 22 against the bronze sheet 19. The adjusting screw 21 is substituted by the shaft 38 which is provided with a thread and driven in the socket 39 by the servo motor 40, through a suitable gear 41. The motor 40 is connected with its remote control means 42 by the cable 43.

In order to adjust the bronze sheet 19 by the remotecontrol means 42 in pre-selected, fixed positions further means 43 known per se, for instance storage means or automatic switch means, are connected with the remotecontrol means 43.

During practical measurements, the phase shifters have turned out to need adjustment only very rarely, nor-' mally only during the first adjustment of the device ac-- cording to the invention. When producing a directionaI pattern of a different kind, it was found that normally only the power dividers had to be adjusted. If necessary, provision may be made for calibration of the adjusting means for the power dividers, or for grid devices corresponding with pre-selected special kinds of patterns, permitting especially fast and simple changes of pattern. Also means, known per se, may be provided for remote-control adjustments, especially of the power dividers.

It will be understood that the above description of the present invention is susceptible to various modifications, changes, and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

What is claimed is:

1. A device for producing a complex directional sec ondary radiation pattern from a reflector, comprising im combination: a plurality of separate exciters arranged in a line and disposed to direct their primary radiations intosaid reflector; a feeder transmission line comprising a supply wave guide means for coupling said exciters to said line, said means including adjustable power dividers associated with respective ones of said exciters for adjusting the amount of power supplied to the particular exciter to which the power divider is connected, said power dividers being connected to said feeder transmission line to allow the power distribution to be varied at any time, including during operation of the device, to produce the particular radiation pattern desired, each adjustable power divider comprising a metal sheet projecting into the supply waveguide at at least one point of connection of a. curved waveguide to the supply waveguide; and phase shifters associated with respective ones of said exciters for adjusting the phase of the particular exciter with which the phase shifter is associated, said phase shifters being variable independently of each other and of said power dividers for achieving a uniform phase front radiated by said exciters.

2. In a device as set forth in claim 1, adjustment means extending through the waveguide and contacting said sheet for adjusting the position thereof in the waveguide from outside.

3. In a device as set forth in claim 2, said adjustment means comprising remote-control means for adjusting the metal sheet.

4. In a device as set forth in claim 2, said adjustment means including insulator pins extending into the waveguide, and said device including means for compensating for interference with the electromagnetic waves caused by the adjusting means and including other insulator pins extending across the waveguide in spaced relation with the first-mentioned pins.

5. In a device as set forth in claim 4, said compensating means comprising pins disposed across the waveguide one: quarter wave length ahead of the pins of said adjustment means.

6. In a device as set forth in claim 1, said sheets being fixed to the sides of the waveguide and having corrugat-ions permitting warping of the centers of the sheets into various positions in the waveguide.

7. In a device as set forth in claim 1, said phase shifters comprising plates of low-loss dielectric material within the supply waveguide.

8. In a device as set forth in claim 7, said phase shifter plates having at least at one end wedge-shaped tapers to reduce reflections therefrom.

9. In a device as set forth in claim 7, said plates being mounted in the waveguide on adjustable means whereby their positions transversely of the waveguide may be ad. justed.

5 10. In a device as set forth in claim 1, said reflector 2,898,593 comprising a parabolic mirror, and the axes of said ex- 2,976,535 citers converging at the focus thereof. 3,016,531

11. A device as set forth in claim 1 wherein said power dividers are infinitely variable. 5

References Cited by the Examiner UNITED STATES PATENTS 6 8/ 1959 Ruze 343-854 3/ 1961 Cutler 343779 1/ 1962 Tomiyasu et a1 34317.1

FOREIGN PATENTS 4/1944 France. 12/1952 France.

2 286 839 6/1942 Shelkunofi X HERMAN KARL SAALBACH, Primary Examiner. 2,464,276 3/1949 Varian 343-768X GEORGE N. WESTBY, Examiner. 2,605,413 7/1952 Alvarez 343-854 X 

1. A DEVICE FOR PRODUCING A COMPLEX DIRECTIONAL SECONDARY RADIATION PATTERN FROM A REFLECTOR, COMPRISING IN COMBINATION: A PLURALITY OF SEPARATE EXCITERS ARRANGED IN A LINE AND DISPOSED TO DIRECT THEIR PRIMARY RADIATIONS INTO SAID REFLECTOR; A FEEDER TRANSMISSION LINE COMPRISING A SUPPLY WAVE GUIDE MEANS FOR COUPLING SAID EXCITERS TO SAID LINE, SAID MEANS INCLUDING ADJUSTABLE POWER DIVIDERS ASSOCIATED WITH RESPECTIVE ONES OF SAID EXCITERS FOR ADJUSTING THE AMOUNT OF POWER SUPPLIED TO THE PARTICULAR EXCITER TO WHICH THE POWER DIVIDER IS CONNECTED, SAID POWER DIVIDERS BEING CONNECTED TO SAID FEEDER TRANSMISSION LINE TO ALLOW THE POWER DISTRIBUTION TO BE VARIED AT ANY TIME, INCLUDING DURING OPERATION OF THE DEVICE, TO PRODUCE THE PARTICULAR RADIATION PATTERN DESIRED, EACH ADJUSTABLE POWER DIVIDER COMPRISING A METAL SHEET PROJECTING INTO THE SUPPLY WAVEGUIDE AT AT LEAST ONE POINT OF CONNECTION OF A CURVED WAVEGUIDE TO THE SUPPLY WAVEGUIDE; AND PHASE SHIFTERS ASSOCIATED WITH RESPECTIVE ONES OF SAID EXCITERS FOR ADJUSTING THE PHASE OF THE PARTICULAR EXCITER WITH WHICH THE PHASE SHIFTER IS ASSOCIATED, SAID PHASE SHIFTERS BEING VARIABLE INDEPENDENTLY OF EACH OTHER AND OF SAID POWER DIVIDERS FOR ACHIEVING A UNIFORM PHASE FRONT RADIATED BY SAID EXCITERS. 